Novel methods to measure the gravitational constant in space

Abstract

We present two novel methods, tested by LISA Pathfinder, to measure the gravitational constant G for the first time in space. Experiment 1 uses electrostatic suspension forces to measure a change in acceleration of a test mass due to a displaced source mass. Experiment 2 measures a change in relative acceleration between two test masses due to a slowly varying fuel tank mass. Experiment 1 gave a value of G ¼ 6.71 AE 0.42ð×10 −11 Þ m 3 s −2 kg −1 and experiment 2 gave 6.15 AE 0.35ð×10 −11 Þ m 3 s −2 kg −1 , both consistent with each other to 1σ and with the CODATA 2014 recommended value of 6.67408 AE 0.00031ð×10 −11 Þ m 3 s −2 kg −1 to 2σ. We outline several ideas to improve the results for a future experiment, and we suggest that a measurement in space would isolate many terrestrial issues that could be responsible for the inconsistencies between recent measurements.

A simple superconductor quantum interference device for testing gravity

“…Even the possibility of simply providing a new way for measuring the Newtonian gravitational attraction is in itself a remarkable feature of our setup. Indeed, the prevailing disagreement between the presently measured values of G [39] makes any new proposal for measuring the latter very attractive [18].…”

“…The smallness of the universal gravitational constant G and the inverse square-law (ISL) -the 1/r 2 -dependence of the gravitational interaction between any two massive objects separated by a distance r -are the main sources of difficulties one faces when attempting to test gravity and its universal constant G to high precision. Any attempt to decrease the separation distance r between the two masses in the hope of making the resulting gravitational force stronger and, hence, easier to be detected, is automatically accompanied by an increase in the strength of the other non-gravitational interactions, such as the van der Waals and Casimir forces to which rapidly add then the electric, the weak and strong nuclear forces that easily overwhelm the gravitational force as one keeps decreasing the separation distance r [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. For this reason researchers have switched to indirect and more subtle tests based on quantum particles that do not rely on the gravitational force between a weakly separated pair of masses [19][20][21][22][23][24][25][26][27].…”

“…region on the Yukawa (α, λ)-plane for α within the interval [10 −4 ∼ 10 8 ] and for λ within the interval [10 −6 m ∼ 10 −2 m]. On the other hand, older[3] and more recent[14][15][16][17][18] spacebased tests allow to put constraints on the Yukawa (α, λ)-plane for α within the interval [10 −10 ∼ 10 −1 ] and for λ within the interval [10 −2 m ∼ 10 14 m]. In all cases, however, the domain in the Yukawa (α, λ)-plane for which α and λ lie below certain regions still remains inaccessible.…”

Variance of Newtonian constant from local gravitational acceleration measurements

“…Second, there are no two identical experiments that have been repeated. Most of the researchers are focusing on new methods, for example in [6]. The National Institute of standards and Technology, the International Union of Pure and Applied Physics, and international Committee for Weight and Measures invested a significant effort in finding the source of the discrepancies [7][8][9].…”

Observable Gravitational Waves in Minimal Scotogenic Model

“…Although the ongoing direct detection experiments have not exhausted all parameter space yet, specially in the context of the minimal scotogenic model, it is equally important to look for complementary probes. One such indirect possibility is to search for gravitational wave (GW) which has gained lots of attention due to planned near future experiments like LISA and other similar space based interferometer experiments [35][36][37][38][39][40][41][42]. A possible source of GW signals is a strong first-order phase transition (SFOPT) where, in particular, GW signals are generated by bubble collisions [43][44][45][46][47], the sound wave of the plasma [48][49][50][51] and the turbulence of the plasma [52][53][54][55][56][57].…”